From: Mina Almasry <almasrymina@google.com> To: Mike Kravetz <mike.kravetz@oracle.com> Cc: shuah <shuah@kernel.org>, open list <linux-kernel@vger.kernel.org>, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, cgroups@vger.kernel.org, Aneesh Kumar <aneesh.kumar@linux.vnet.ibm.com> Subject: Re: [PATCH v8 5/9] hugetlb: disable region_add file_region coalescing Date: Mon, 4 Nov 2019 13:19:18 -0800 [thread overview] Message-ID: <CAHS8izMYaHf-3zeVcM_73_KSMCpA5vds-NtRjNt0d8VsMfczQw@mail.gmail.com> (raw) In-Reply-To: <a5f991c8-3f74-6000-cbd3-09fb8626e3f5@oracle.com> On Mon, Nov 4, 2019 at 1:15 PM Mike Kravetz <mike.kravetz@oracle.com> wrote: > > On 11/4/19 1:04 PM, Mina Almasry wrote: > > On Fri, Nov 1, 2019 at 4:23 PM Mike Kravetz <mike.kravetz@oracle.com> wrote: > >> > >> On 10/29/19 6:36 PM, Mina Almasry wrote: > >>> static long add_reservation_in_range(struct resv_map *resv, long f, long t, > >>> - bool count_only) > >>> + long *regions_needed, bool count_only) > >>> { > >>> - long chg = 0; > >>> + long add = 0; > >>> struct list_head *head = &resv->regions; > >>> + long last_accounted_offset = f; > >>> struct file_region *rg = NULL, *trg = NULL, *nrg = NULL; > >>> > >>> - /* Locate the region we are before or in. */ > >>> - list_for_each_entry (rg, head, link) > >>> - if (f <= rg->to) > >>> - break; > >>> + if (regions_needed) > >>> + *regions_needed = 0; > >>> > >>> - /* Round our left edge to the current segment if it encloses us. */ > >>> - if (f > rg->from) > >>> - f = rg->from; > >>> - > >>> - chg = t - f; > >>> + /* In this loop, we essentially handle an entry for the range > >>> + * [last_accounted_offset, rg->from), at every iteration, with some > >>> + * bounds checking. > >>> + */ > >>> + list_for_each_entry_safe(rg, trg, head, link) { > >>> + /* Skip irrelevant regions that start before our range. */ > >>> + if (rg->from < f) { > >>> + /* If this region ends after the last accounted offset, > >>> + * then we need to update last_accounted_offset. > >>> + */ > >>> + if (rg->to > last_accounted_offset) > >>> + last_accounted_offset = rg->to; > >>> + continue; > >>> + } > >>> > >>> - /* Check for and consume any regions we now overlap with. */ > >>> - nrg = rg; > >>> - list_for_each_entry_safe (rg, trg, rg->link.prev, link) { > >>> - if (&rg->link == head) > >>> - break; > >>> + /* When we find a region that starts beyond our range, we've > >>> + * finished. > >>> + */ > >>> if (rg->from > t) > >>> break; > >>> > >>> - /* We overlap with this area, if it extends further than > >>> - * us then we must extend ourselves. Account for its > >>> - * existing reservation. > >>> + /* Add an entry for last_accounted_offset -> rg->from, and > >>> + * update last_accounted_offset. > >>> */ > >>> - if (rg->to > t) { > >>> - chg += rg->to - t; > >>> - t = rg->to; > >>> + if (rg->from > last_accounted_offset) { > >>> + add += rg->from - last_accounted_offset; > >>> + if (!count_only) { > >>> + nrg = get_file_region_entry_from_cache( > >>> + resv, last_accounted_offset, rg->from); > >>> + list_add(&nrg->link, rg->link.prev); > >>> + } else if (regions_needed) > >>> + *regions_needed += 1; > >>> } > >>> - chg -= rg->to - rg->from; > >>> > >>> - if (!count_only && rg != nrg) { > >>> - list_del(&rg->link); > >>> - kfree(rg); > >>> - } > >>> + last_accounted_offset = rg->to; > >> > >> That last assignment is unneeded. Correct? > >> > > > > Not to make you nervous, but this assignment is needed. > > > > The basic idea is that there are 2 loop invariants here: > > 1. Everything before last_accounted_offset is filled in with file_regions. > > 2. rg points to the first region past last_account_offset. > > > > Each loop iteration compares rg->from to last_accounted_offset, and if > > there is a gap, it creates a new region to fill this gap. Then this > > assignment restores loop invariant #2 by assigning > > last_accounted_offset to rg->to, since now everything before rg->to is > > filled in with file_regions. > > > > My apologies! > > >>> } > >>> > >>> - if (!count_only) { > >>> - nrg->from = f; > >>> - nrg->to = t; > >>> + /* Handle the case where our range extends beyond > >>> + * last_accounted_offset. > >>> + */ > >>> + if (last_accounted_offset < t) { > >>> + add += t - last_accounted_offset; > >>> + if (!count_only) { > >>> + nrg = get_file_region_entry_from_cache( > >>> + resv, last_accounted_offset, t); > >>> + list_add(&nrg->link, rg->link.prev); > >>> + } else if (regions_needed) > >>> + *regions_needed += 1; > >>> + last_accounted_offset = t; > > The question about an unnecessary assignment was supposed to be > directed at the above line. > Oh, yes. That assignment is completely unnecessary; the function just exits after pretty much. Will remove, thanks! > -- > Mike Kravetz > > > >>> } > >>> > >>> - return chg; > >>> + return add; > >>> }
next prev parent reply other threads:[~2019-11-04 21:19 UTC|newest] Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-10-30 1:36 [PATCH v8 1/9] hugetlb_cgroup: Add hugetlb_cgroup reservation counter Mina Almasry 2019-10-30 1:36 ` [PATCH v8 2/9] hugetlb_cgroup: add interface for charge/uncharge hugetlb reservations Mina Almasry 2019-11-08 0:57 ` Mike Kravetz 2019-11-08 23:48 ` Mina Almasry 2019-11-09 0:01 ` Mike Kravetz 2019-11-09 0:40 ` Mina Almasry 2019-11-09 0:46 ` Mike Kravetz 2019-11-25 20:26 ` Mina Almasry 2019-11-26 0:05 ` Mike Kravetz 2019-10-30 1:36 ` [PATCH v8 3/9] hugetlb_cgroup: add cgroup-v2 support Mina Almasry 2019-10-30 1:36 ` [PATCH v8 4/9] hugetlb_cgroup: add reservation accounting for private mappings Mina Almasry 2019-10-30 1:36 ` [PATCH v8 5/9] hugetlb: disable region_add file_region coalescing Mina Almasry 2019-11-01 23:23 ` Mike Kravetz 2019-11-04 21:04 ` Mina Almasry 2019-11-04 21:15 ` Mike Kravetz 2019-11-04 21:19 ` Mina Almasry [this message] 2019-11-17 11:03 ` Wenkuan Wang 2019-11-18 19:41 ` Mina Almasry 2019-10-30 1:36 ` [PATCH v8 6/9] hugetlb_cgroup: add accounting for shared mappings Mina Almasry 2019-10-30 1:36 ` [PATCH v8 7/9] hugetlb_cgroup: support noreserve mappings Mina Almasry 2019-10-30 1:37 ` [PATCH v8 8/9] hugetlb_cgroup: Add hugetlb_cgroup reservation tests Mina Almasry 2019-10-30 1:37 ` [PATCH v8 9/9] hugetlb_cgroup: Add hugetlb_cgroup reservation docs Mina Almasry 2019-11-07 23:42 ` [PATCH v8 1/9] hugetlb_cgroup: Add hugetlb_cgroup reservation counter Mike Kravetz 2019-11-08 23:35 ` Mina Almasry
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